If your preamp was a very old AVA model, you probably have nothing much to worry about. Years ago we got a large batch of Noble volume and balance controls in which a little Japanese workman had the task of installing the "detent spring" into the controls and fastening it into place by dropping it onto a small raised peg in the front section of the control body and then smashing the peg flat, thus riveting the spring into place. This particular workman did not "smash" hard enough. After years of use of the control, the little spring would work loose from its only slightly smashed peg and pop out of place, thus disabling the detent function. This appears to have happened to your control, Mark.
Since the detent function is in a separate internal compartment in the control body than the active elements, it will have no electrical effect on the control, only with the detent feel.
Our cure, once we figured out the problem only several years after the fact, was to take apart every Noble volume control we used before installing them and smash the detent spring rivet really flat so it would never come apart. This was a pain in the ass job but oh well, it had to be done. We can also do this to units that have lost their detents because they were shipped before the problem started happening. Its about an hour of labor to do and in the EC preamp involves dropping the switch circuit board to access them.
In recent years we have switched to precision ALPs pots and have had zero problems with them.
Regards,
Frank Van Alstine
